Normally, the traffic surrounding an aircraft is represented onboard that aircraft on a display screen that, more often than not, indicates a position in plan mode, of the PPI (Plan Position Indicator) type, illustrating a graphical representation in the horizontal plane of the aeronautical surroundings of the aircraft. Such a display mode enables the pilot of the aircraft to easily identify the bearing and the distance of the aircraft in the vicinity displayed, but, however, not their vertical position. Also, to overcome this oversight, there are also normally displayed numerical values (relative or absolute) indicating the altitudes of the various aircraft in the vicinity. However, such a numerical representation of the altitude (or vertical position), associated with the abovementioned graphical representation (which is far more intuitive) of the horizontal position, makes understanding and perceiving the real position of the various aircraft in the vicinity difficult for the pilot. This display mode involves in particular a significant workload and a significant time to enable the pilot to mentally integrate the actual situation of the air environment of his aircraft.